There are two basic forms of coatings that are typically applied to circuit boards. These coatings include beads of material applied to specific locations on the circuit board, and substantially uniform thickness coatings applied over large sections of the circuit board. The coatings may comprise a wide variety of materials such as ultraviolet (UV) acrylic gels, moisture and thermal cure silicones, and the like.
The coatings are typically applied to a circuit board using devices such as spray guns, spray nozzles, or dispensing nozzles. For spraying, such devices generally include a liquid spray material that is atomized by compressed air and is then directed toward the surface to be coated. For dispensing, such devices generally include a pressurized liquid material that is dispensed through a nozzle tip in close proximity to the surface being coated.
In many applications, including the coating of a circuit board, both a spraying and a dispensing device are required. The spraying and dispensing devices are commonly attached to an apparatus, such as a multi-degree of freedom robotic positioning apparatus, that provides accurate positional displacement relative to the article being coated.
Having two separate devices, one for spraying and one for dispensing, however, greatly increases the complexity and cost of the coating process. Also, since the spraying and dispensing devices are generally mounted on opposing sides of a single arm of the robotic positioning apparatus, the surface area that is accessible is limited by the interference of one or both of the devices at the boundaries of the positioning apparatus. Production setup time and maintenance time are also increased, and, if spraying and dispensing is required at the same location on the surface, the time required to reposition the spraying and dispensing devices is increased.